Technique for de-orbiting small debris from the near-earth space environment

ABSTRACT

System and method for inducing rapid reentry of orbital debris including determining a spatial extent of the orbital debris, and deploying dust to the orbital debris to enhance the drag on the orbital debris. Small objects with perigee above about 900 km where the debris lifetime can be centuries can be targeted for de-orbiting.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a continuation of U.S. patent application Ser. No.13/017,813 entitled A TECHNIQUE FOR DE-ORBITING SMALL DEBRIS FROM THENEAR-EARTH SPACE ENVIRONMENT, filed on Jan. 31, 2011, which is anonprovisional application of provisional application 61/300,871,entitled A TECHNIQUE FOR DE-ORBITING SMALL DEBRIS FROM THE NEAR-EARTHSPACE ENVIRONMENT, filed on Feb. 3, 2010, under 35 USC 119(e), theentire disclosures of which are incorporated herein by reference.

BACKGROUND

Methods and systems disclosed herein relate generally to de-orbitingobjects in outer space, and in particular, de-orbiting debris from thehighly populated sun synchronous orbit region by injecting micron scaledust grains in this region. Small objects, for example, but not limitedto, space debris, can be difficult to track individually and remove,thus making small objects possibly dangerous to other orbiting objects.Referring now to FIG. 1, orbital debris with characteristic size of10-1000 cm are shown to be far less numerous than orbital debris withcharacteristic size smaller than 10 cm. The small object population islocalized at an altitude around 1000 km and between 50-100 degrees ininclination angle. The approximate lifetime of these small objects withperigee of 800 km or less and having a ballistic coefficient of three orless is approximately 25 years or less due to natural atmospheric drag.In an effort to reduce future accumulation of orbital debris, U.S.Government guidelines specify that space objects are to be de-orbitedwithin 25 years of mission completion. (see “Process for LimitingOrbital Debris”, NASA-STD 8719.14, published in 2007). Thus, what isneeded is to relocate the orbits of the small object populations thatpeak around 1000 km altitude, that have lifetimes of centuries, to belowan altitude so that they can be naturally de-orbited within 25 years orless. Space objects such as debris can be broadly classified into twocategories: (i) large objects with dimension larger than 10 cm and (ii)small objects with dimension smaller than 10 cm. The smaller debris canbe more numerous and can be difficult to detect and can be impossible toindividually track. These characteristics can make them more dangerousthan the fewer larger objects that can be tracked and hence avoided. Inaddition, there are several solutions for addressing larger objects, forexample, DARPA/NRL's FREND device that can remove large objects fromuseful orbits and place them in graveyard orbits. However, damage fromcentimeter to millimeter size objects can be dangerous.

Referring now to FIG. 2A, a 4 mm diameter crater on the windshield ofthe Space Shuttle was created by impact of 0.2 mm paint chip. Referringnow to FIG. 2B, a hole on an antenna of the Hubble space telescope wascreated by the impact of an object of less than 1 cm. These collisionscould create vulnerability in space operations that could become moresevere in the future. What is needed is a small object removal systemand method that can address this vulnerability and that could ensureuninterrupted access to the near-earth space.

Referring now to FIG. 3A, an exemplary tracked object population isshown to be localized within about 50° of inclination angle. Referringnow to FIG. 3B, objects in sun synchronous orbits, where most of theorbital debris is located, have nearly circular orbits. The largertrackable debris peaks around 800 km altitude. Referring now to FIG. 4,the smaller objects, although difficult to track individually, can betracked statistically and the resulting distribution is roughly similarto the tracked objects shown in FIG. 3B but peaks at higher (˜1000 km)altitude. Referring now to FIG. 5, the orbital lifetimes of objects as afunction of their ballistic coefficient (B), defined as the mass to arearatio, are shown. Objects with B˜3 peak around 1000 km and theirlifetimes become 25 years or less below 900 km. Above 900 km thelifetimes can become centuries. Therefore, the task of small objectremoval is essentially to reduce the object orbit height from around1100 km to below 900 km and then let nature take its course. For fasterremoval in less than 25 years the debris altitude may be loweredfarther. There are about 900 active satellites and about 19,000earth-orbiting cataloged objects larger than 10 cm. However, there arecountless smaller objects that can be difficult to track individually.Unintentional (collision or explosion) or intentional fragmentation ofsatellites can increase the object population significantly. Forexample, the 2007 Chinese Anti-Satellite test generated 2400 largeobjects and countless smaller ones in the very popular sun synchronousorbit at about 865 km altitude. A similar increase of object populationalso resulted from the 2009 collision of an Iridium satellite with aspent Russian satellite. The object population is expected to risesubstantially as more and more nations become space faring.

What are needed are a system and method to induce rapid reentry oforbital debris.

SUMMARY

To address the above-stated need, small objects with B˜3-5 in orbitswith perigee above about 900 km where the debris lifetime can becenturies can be targeted for de-orbiting. A method for inducing rapidreentry of orbital debris can include, but is not limited to including,the steps of determining a spatial extent of the orbital debris to betargeted, where the orbital debris has a first edge that is at a higheraltitude than a second edge of the orbital debris, and deploying dust tothe location to enhance the drag on the orbital debris. There are atleast two ways to deploy the dust, through orbiting satellites andthrough ballistic methods shown, for example, in FIGS. 6A-6C and 7A-7C.The satellite method of deploying can include, but is not limited toincluding, the steps of determining the debris orbit of the orbitaldebris, selecting at least one satellite, the at least one satellitecounter-orbiting with respect to the debris orbit, configuring the atleast one satellite with the dust, and configuring the at least onesatellite to release the dust in the debris orbit at the higher altitudeedge of the orbital debris, the dust being released in a directioncounter-rotating to the debris orbit. The ballistic method of deployingcan include, but is not limited to including, the steps of determining aforward edge of the orbital debris, determining a forward edge locationat a pre-selected time, equipping a space vehicle with the dust,launching the space vehicle to arrive at the forward edge locationbefore the pre-selected time, and configuring the space vehicle torelease the dust at the forward edge location at the pre-selected timeto engulf the orbital debris as the orbital debris passes through thedust. Either method can further include the steps of selecting the dustbased on dust properties, the dust properties at least minimizingadverse effects on active satellites, the dust properties causing anatural rate of decay of the orbit altitude of the dust to be roughlysynchronized with a rate of artificial decay of the orbital debris,determining an amount of the dust based on the spatial extent of a dustcloud of the dust, the position of the orbital debris, and the amount oftime of the interaction of the cloud with the orbital debris,determining the lifetime of the dust based on the dust properties,characteristics of the dust cloud, and solar radiation pressure on dustcloud, adjusting the density of the dust to include effects only on apre-selected subset of the orbital debris, and lowering the altitude ofthe orbital debris to a desired altitude depending on their ballisticcoefficients below which earth's natural drag is sufficient to de-orbitthe debris within a desired time.

A system for inducing rapid reentry of orbital debris can include, butis not limited to including, a debris location processor for determininga spatial extent of the orbital debris, and a deployment processor fordeploying dust to the orbital debris of the spatial extent toartificially enhance the drag on the orbital debris. The deploymentprocessor can be, for example, but not limited to, a ballisticdeployment processor or a satellite deployment processor. The ballisticdeployment processor can include, but is not limited to including, aforward edge subprocessor for determining from the spatial extent of theorbital debris a forward edge of the orbital debris, and a timeprocessor for determining a forward edge location of the forward edge ata pre-selected time. The ballistic deployment processor can also includea space vehicle subprocessor configured to equip a space vehicle withthe dust, a launch subprocessor configured to launch the space vehicleto arrive at the forward edge location before the pre-selected time, anda release subprocessor configured to release the dust at the forwardedge location at the pre-selected time to engulf the orbital debris asthe orbital debris passes through the dust cloud. The satellitedeployment processor can include, but is not limited to including, anorbit subprocessor for determining an orbit altitude band of the orbitaldebris of the spatial extent, a satellite selection subprocessor forselecting at least one satellite, the at least one satellitecounter-orbiting with respect to the debris orbit, and a satelliteconfiguration processor for configuring the at least one satellite withthe dust, and for configuring the at least one satellite to release thedust in the orbit altitude band at the higher altitude edge of theorbital debris, the dust being released in a direction counter-rotatingin relation to at least a portion of a distributed band of the orbitaldebris. The system can further include subprocessor for selecting thedust based on dust properties, the dust properties at least minimizingadverse effects on active satellites, the dust properties causing anatural rate of decay of the orbit altitude of the dust to be roughlysynchronized with a rate of artificial decay of the orbital debris, fordetermining an amount of the dust based on the spatial extent of a dustcloud of the dust, the position of the orbital debris, and the amount oftime of the interaction of the cloud with the orbital debris, fordetermining the lifetime of the dust based on the dust properties,characteristics of the dust cloud, and solar radiation pressure on dustcloud, for adjusting the density of the dust to effect a subset of theorbital debris, for example, but not limited to, a subset having apre-selected ballistic coefficient range, and for lowering the altitudeof the orbital debris to a pre-selected altitude, the pre-selectedaltitude being sufficient to deorbit the orbital debris based on theEarth's natural drag in the desired time.

For example, small objects with a ballistic coefficient(mass(kg)/area(m²)) of three or less can be evaluated. A ballisticcoefficient of three represents small objects in a variety of sizes andshapes, for example, broken pieces of satellites, for example, but notlimited to, aluminum having a density 2.7 gm/cc and with 10 cm×10 cmsurface area exposed to the drag force. Objects with lower density, forexample, but not limited to, plastic having a density of 1 gm/cc can belarger in dimension. The dust density necessary to de-orbit smallobjects can be sufficiently low such that the orbits of larger activesatellites with much larger ballistic coefficients can be minimallyaffected. The size and material of dust grains can be optimized toobtain the desired dust layer lifetime in orbit and to minimize impactdamage to active satellites.

Exemplary analysis using circular orbits indicates that objects withballistic coefficient of three or less can be de-orbited from 1100 km to900 km in twenty-five years using, for example, but not limited to,twelve tons of tungsten dust of about 10-30 μm diameter. A largerquantity of dust may be used, for example, for a larger altitudereduction or when the orbital debris has a relatively large ballisticcoefficient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical representation of the number of orbital debrisobjects found within 1600 km of the Earth's surface;

FIG. 2A is a pictorial representation of a 4 mm diameter crater on thewindshield of the space shuttle created by the impact of a 0.2 mm paintchip;

FIG. 2B is a pictorial representation that the impact of a <1 cm pieceof orbital debris created a hole on an antenna of the Hubble spacetelescope;

FIG. 3A is a graphical representation of the debris distribution ininclination angles;

FIG. 3B is a graphical representation of showing that most of theobjects in the sun synchronous orbits have nearly circular orbits;

FIG. 4 is a graphical representation of statistical tracking of smallobjects;

FIG. 5 is a graphical representation of the lifetimes of objects as afunction of their ballistic coefficients;

FIGS. 6A-6C are diagrams illustrating the ballistic method ofdeployment;

FIGS. 7A-7C are diagrams illustrating the satellite method ofdeployment;

FIGS. 8A and 8B are schematic block diagrams of the system for inducingrapid reentry of orbital debris; and

FIGS. 9A-9C are flowcharts of the methods for inducing rapid reentry oforbital debris of the present teachings.

DETAILED DESCRIPTION

The problems set forth above as well as further and other problems aresolved by the present teachings. These solutions and other advantagesare achieved by the various embodiments of the teachings describedherein below.

The altitude of objects, referred to herein as orbital debris, can bereduced to below 900 km by artificially increasing the drag on theobjects. Higher drag can be achieved by dust grains in a similar butoppositely directed orbit with respect to the targeted objects. Due toorbit perturbations caused by the Earth's irregular gravitational field,the dust as well as objects' orbits can precess and intersect withdifferent objects at both head-on and grazing angles. As result ofprecession and some spread in velocity the dust grains injected inquasi-circular orbits ultimately form an azimuthal shell or a partialshell.

Referring now to FIGS. 6A-6C and FIGS. 7A-7C, satellite method 250 (FIG.9B) and ballistic method 350 (FIG. 9C) are pictorially illustrated.FIGS. 6A-6C illustrate a dust cloud in a polar orbit counter-rotatingwith respect to the debris. FIG. 6A illustrates a targeted debrispopulation located in a shell between altitudes X1 and X2 (shaded). Inthe drawing, a torroidal dust cloud of thickness δR is deployed in polarorbit at the upper edge of the debris band (darker shades). FIG. 6Billustrates that half of the debris population is counter-rotating withrespect to the dust. This leads to enhanced drag on the debris resultingin loss of debris altitude. The dust orbit also descends under Earth'snatural drag. Dust sweeps the debris population with it and leads to adust “snow plow” effect. FIG. 6C illustrates that the descents of thedust cloud and the debris population can be synchronized. Both dust anddebris descend to an altitude of x0 km below which Earth's natural dragis sufficient to force reentry within a desired time. FIGS. 7A-7Cillustrate orbital debris intersecting with ballistically injected dustand being de-orbited.

The drag on the objects' orbit is determined by,

$\begin{matrix}{{{\underset{\underset{\underset{Coefficient}{Ballistic}}{︸}}{\left( \frac{M}{A^{2}} \right)}\frac{\mathbb{d}V}{\mathbb{d}t}} = {{{- \underset{\underset{Dust}{︸}}{n_{d}m_{d}}} \times \underset{\underset{\underset{Velocity}{Relative}}{︸}}{\left( {V - v_{d}} \right)^{2}} \times \kappa} - {\underset{\underset{Atmosphere}{︸}}{n_{0}m_{0}}V^{2}}}},} & (1)\end{matrix}$where M, A, V, are debris mass, representative linear dimension, andvelocity, while m_(d), v_(d), and n_(d), are the mass, velocity, anddensity of dust. For circular orbits the change in velocity and altitudeis related by ΔR=2R(ΔV/V). The factor κ=(1+√{square root over (1+f)}) inEq. (1) accounts for the type of dust/objects collision. If f=−1 then itimplies that the dust is stuck on the objects on impact i.e., inelasticcollision, f=0 implies elastic collision, and f>0 implies loss of debrismass due to evaporation or melting resulting from hypervelocity impacts.The natural atmospheric drag is included in Eq. (1) through atmosphericdensity n₀ and mass m₀. By considering a thin layer of dust of width δR,Eq. (1) indicates that the total dust mass M_(d) necessary to reduce theobjects' height from its location at R by ΔR is,

$\begin{matrix}{{\left. M_{d} \right.\sim B}\;\frac{2\pi\; R^{2}\delta\; R}{{\kappa\left( {V - v_{d}} \right)}^{2}}\frac{\mathbb{d}R}{\mathbb{d}t}} & (2)\end{matrix}$where dR/dt is the rate of debris descent. The dust mass necessary toclear small debris with B<3 located in a spherical shell of width δR=50km at an altitude 1100 km, i.e., R≈7500 km with volume 4 πR²δR=3.5×10⁹km³ in 25 years is three tons for κ=4.3. Maximum drag is achieved whenthe relative velocity between dust and the objects, v_(rel)=V−v_(d)=2Vwhere V≈7.5 km/s. This implies hypervelocity dust-object collision at 15km/s which can result in object evaporation and increase in drag forceby a factor κ=(1+√{square root over (1+f)}), where fin_(d) is the objectmass that can evaporate at hypervelocity impact with dust grain. Forexample, if the object is aluminum with heat of vaporization of 11 KJ/g,dust grains moving at 15 km/s correspond to 110 KJ/g specific kineticenergy. Due to the shock generated at hypervelocity impact, dust kineticenergy will be used to vaporize objects, and object mass of about 10m_(d) can evaporate upon impact. This corresponds to f=10 and henceκ=(1+√{square root over (1+f)})=4.3. This value of κ may be conservativebecause the heat of vaporization of aluminum used corresponds to normalatmospheric pressure. Hypervelocity impact may generate much higherpressure locally which will lower the heat of vaporization leading tomuch larger object matter vaporization. Also the heat of melting islower, implying that a portion of the object will melt and lose moremass than is estimated from vaporization. This will result in larger κwhich implies lower dust mass. Then Eq. (2) indicates that the totaldust mass M_(d) necessary to reduce the object height from its locationat R by ΔR=200 km by a dust “snow plow” effect where the rate of descentof dust layer and the debris is roughly synchronized and isapproximately twelve tons in twenty-five years.

The length of time required to de-orbit the small objects can be limitedby a number of factors. The lifetime of silicon and tungsten dust of avariety of sizes from 1-100 μm can be calculated because the lifetime ofthe dust is proportional to its size. The on/off radiation pressure dueto dust orbit in sunlight and in earth shadow can introduce a spatialspread perpendicular to its Keplerian orbit. Preliminary estimatessuggest that 30 μm or smaller tungsten dust can be suitable for smalldebris de-orbit. The lifetime of 30 μm diameter tungsten dust grainsreleased at an altitude of 1100 km with inclination of 80-90 degrees isabout 15 years.

Based on the physics discussed above, dust can be released inquasi-circular orbits between 900 km and 1100 km. The mass of the dustcan be based on the ballistic coefficient of the objects targeted forremoval. The dimensions of the dust grains can be optimized so that theyare small enough to be harmless to active satellites on impact. Also,the density of the dust grains can be optimized to be sufficient tode-orbit the low ballistic coefficient objects without materiallyaffecting the orbits of active satellites with larger ballisticcoefficient. The period of induced drag on targeted small objects can bedesigned to be long (20-25 years) so that the requirement for the totaldust mass can be low. Since typical lifetime of low earth orbitingsatellites is about 5-7 years and their ballistic coefficient is muchlarger, perturbation to their orbits by the dust during this period maybe negligible. Dust cloud can be released in the form of a torus or apartial torus in the polar orbit. Because of precession the debrisorbits will intersect with the dust torus. In a series of releases inquasi-circular orbits with different inclinations around 90 degrees, thedust cloud can be spread and form an azimuthal shell or a partial shellwith large meridianal velocity in both directions. At any given point inthis shell, half of the dust mass can be in orbit oppositely directed tothe targeted object population. The interaction of dust with objects inthis shell can lower the objects' altitude. The dust layer itself candescend in altitude over time and in the process can lower the altitudeof the objects from 1100 km to 900 km by a “snow plow” effect belowwhich the lifetime of the small objects is naturally 25 years. Alongwith the objects, the injected dust can ultimately burn up in theearth's atmosphere at lower altitudes. The dust may be delivered as asecondary payload utilizing the excess capacity in many launches or as aseparate dedicated dust dispensing satellite.

Since solar arrays returned to earth after years of exposure to the LEOdebris environment on the Hubble Space Telescope have shown the abilityto continue to function without impact attributed power loss despite2,700 impact sites in the 100 micron and above size range, adverseeffects of less than 30 μm dust size to be used for debris removal maybe minimal. Hypervelocity impact of the injected dust with other sensorsof active satellites can occur if the sensors point in the direction ofthe satellite motion, but normally, earth observation satellites pointsensors earthward and scientific satellites point sensors away fromearth, both directions being nearly orthogonal to the satellite motion.Hence, the risk to active satellite missions associated with the smallobjects removal technique of the present teachings is minimized.However, these issues can be circumvented by maneuvering the activesatellites around the dust layer of a limited thickness (−30-50 km).Active spacecraft could be maneuvered above or below this band usingonboard propulsion and avoid the artificial dust flux altogether. Thedelta V required for a 50 km orbit raise is only 44 m/s. For a satellitesuch as DMSP which masses about 825 kg, a 44 m/s orbit raise (plus theslight inclination change needed to maintain sun synchronicity) wouldrequire about 16 kg of hydrazine propellant.

To deploy the dust, canisters can be mass produced and delivered toorbit with any excess capability on, for example, but not limited to, anEvolved Expendable Launch Vehicle (EELV) going into polar orbit. Ifthere are two EELV's (or equivalent) with excess capability launched inpolar orbit per year, and if 150 kg of the 181 kg capacity of each EELVSecondary Payload Adapter (ESPA) ring port can be dust mass, and if allsix ports on an ESPA ring on each of the two assumed polar orbitlaunches per year are used, about 900 kg (roughly a ton) of dust couldbe carried per launch. In five years, approximately 10 tons of dustcould be delivered to polar orbit and in ten years, approximately twentytons.

Referring now to FIGS. 8A and 8B, system 100 for inducing rapid reentryof orbital debris can include, but is not limited to including, debrislocation processor 11 receiving, from debris tracker 10, orbital debrisinformation 37, and determining spatial extent 39 of the orbital debris.System 100 can further include debris processor 13 configured to receivespatial extent 39 from debris location processor 11, and determine dustproperties 41 of the orbital debris of spatial extent 39. System 100 canfurther include deployment processor 15 for deploying dust having dustproperties 41 to the orbital debris having spatial extent 39 toartificially enhance the drag on the orbital debris having spatialextent 39. Deployment processor 15 can receive deployment type 43 todirect deployment processor 15 to choose between, for example, but notlimited to, ballistic deployment processor 17 or satellite deploymentprocessor 19. Ballistic deployment processor 17 can include, but is notlimited to including, forward edge subprocessor 21 for determiningforward edge 45 of the orbital debris, and time processor 23 fordetermining forward edge location 47 of forward edge 45 at apre-selected time 43. Ballistic deployment processor 17 can also includespace vehicle subprocessor 22 configured to equip a space vehicle withthe dust, launch subprocessor 27 configured to launch the space vehicleto arrive at forward edge location 47 before pre-selected time 43, andrelease subprocessor 29 configured to release the dust at forward edgelocation 47 at pre-selected time 43 to engulf the orbital debris as theorbital debris passes through the dust. Satellite deployment processor19 can include, but is not limited to including, orbit subprocessor 31for determining an orbit altitude band of the orbital debris of spatialextent 39, satellite selection subprocessor 33 for selecting at leastone satellite 49 that is counter-orbiting with respect to the debrisorbit, and satellite configuration processor 35 for configuring at leastone satellite 49 with the dust, and for configuring at least onesatellite 49 to release the dust in the debris orbit at the higheraltitude edge of the orbital debris, the dust being released in acounter-rotating orbit relative to the debris orbit. The system canfurther include subprocessors for selecting the dust based on dustproperties 41, where dust properties 41 at least minimize adverseeffects on active satellites, and where dust properties 41 can cause anatural rate of decay of the orbit altitude of the dust to be roughlysynchronized with a rate of artificial decay of the orbital debris, fordetermining an amount of the dust based on the spatial extent of a dustcloud of the dust, the position of the orbital debris, and the amount oftime of the interaction of the cloud with the orbital debris, fordetermining the lifetime of the dust based on dust properties 41,characteristics of the dust cloud, and solar radiation pressureassociated with the dust cloud, for adjusting the density of the dust toeffect a subset of the orbital debris, for example, a subset having apre-selected ballistic coefficient range, and for lowering the altitudeof the orbital debris to a pre-selected altitude, the pre-selectedaltitude being sufficient to deorbit the orbital debris based on theEarth's natural drag in the desired time.

Referring now primarily to FIGS. 9A-9C, method 150 for inducing rapidreentry of orbital debris can include, but is not limited to including,the steps of determining 101 spatial extent 39 (FIG. 8B) of the orbitaldebris, and deploying 103 dust to the orbital debris of spatial extent39 (FIG. 8B) to artificially enhance the drag on the orbital debris.There are at least two methods to deploy the dust, satellite method 250and ballistic method 350. Satellite method 250 of deploying dust caninclude, but is not limited to including, the steps of determining 201an orbit altitude band of the orbital debris of spatial extent 39 (FIG.8B), selecting 203 a satellite that is in a counter-orbit with respectto the orbit of the orbital debris, configuring 205 the satellite toinclude the dust, and configuring 207 the satellite to release the dustinto the orbit altitude band at the higher altitude edge of the orbitaldebris, the dust being released in a direction counter-rotating inrelation to at least a portion of a distributed band of the orbitaldebris orbit (see FIGS. 6A-6C). Ballistic method 350 of deploying caninclude, but is not limited to including, the steps of determining 301from spatial extent 39 (FIG. 8B) forward edge 45 (FIG. 8B) of theorbital debris, determining 303 forward edge location 47 (FIG. 8B) offorward edge 45 (FIG. 8B) at pre-selected time 43 (FIG. 8B), equipping305 a space vehicle with the dust, launching 307 the space vehicle toarrive at forward edge location 47 (FIG. 8B) before pre-selected time 43(FIG. 8B), and configuring 309 the space vehicle to release the dust atforward edge location 47 (FIG. 8B) at pre-selected time 43 (FIG. 8B) toengulf the orbital debris as the orbital debris passes through the dust.Either satellite method 250 or ballistic method 350 can further includethe steps of selecting the dust based on dust properties 41 (FIG. 8B),so that the dust at least minimizes adverse effects on satellites,determining an amount of the dust based on the spatial extent of a cloudof the dust, the position of the orbital debris, and the amount of timeof the interaction of the cloud with the orbital debris based on dustproperties 41 (FIG. 8B), characteristics of the dust cloud, adjustingthe density of the dust to effect a subset of the orbital debris, forexample, the subset having a pre-selected ballistic coefficient range,and lowering the altitude of the orbital debris to a pre-selectedaltitude, the pre-selected altitude being sufficient to deorbit theorbital debris based on the Earth's natural drag in the desired time.Satellite method 250 can further include the steps of selecting the dustbased on dust properties, the dust properties being configured to causea natural rate of decay of the orbit altitude of the dust to be roughlysynchronized with a rate of artificial decay of the orbital debris, anddetermining the lifetime of the dust based on solar radiation pressureon the dust cloud.

The present embodiment is also directed to a system and methods that canbe executed in hardware, firmware, and/or software for accomplishing themethods discussed herein, and, possibly, computer readable media storingsoftware for accomplishing these methods and system. The various modulesdescribed herein can be provided in conjunction with a single CPU, or onan arbitrary number of different CPUs. Other alternative computerplatforms can be used. The operating system can be, for example, but isnot limited to, WINDOWS® or LINUX®. Communications links can be wired orwireless, for example, using cellular communication systems, militarycommunications systems, and satellite communications systems. Any dataand results can be stored for future retrieval and processing, printed,displayed, transferred to another computer, and/or transferredelsewhere.

In compliance with the statute, the present embodiment has beendescribed in language more or less specific as to structural andmethodical features. It is to be understood, however, that the presentembodiment is not limited to the specific features shown and described,since the means herein disclosed comprise preferred forms of putting thepresent embodiment into effect.

Referring again to FIGS. 9A-9C, methods 150, 250, and 350 can be, inwhole or in part, implemented electronically. Signals representingactions taken by elements of system 100 and other disclosed embodimentscan travel over at least one live communications network. Control anddata information can be electronically executed and stored on at leastone computer-readable medium. The system can be implemented to executeon at least one computer node in at least one live communicationsnetwork. Common forms of at least one computer-readable medium caninclude, for example, but not be limited to, a floppy disk, a flexibledisk, a hard disk, magnetic tape, or any other magnetic medium, acompact disk read only memory or any other optical medium, punchedcards, paper tape, or any other physical medium with patterns of holes,a random access memory, a programmable read only memory, and erasableprogrammable read only memory (EPROM), a Flash EPROM, or any othermemory chip or cartridge, or any other medium from which a computer canread.

Although the present teachings have been described with respect tovarious embodiments, it should be realized these teachings are alsocapable of a wide variety of further and other embodiments.

What is claimed is:
 1. A method for inducing rapid reentry of adistribution of orbital debris scattered over a large volume comprising:determining a forward edge location of the distribution of orbitaldebris; and intentionally deploying, from a spacecraft, a specific kindof dust in a series of non-forceful releases, the specific kind of dustintersecting the forward edge location of the distribution of orbitaldebris, the specific kind of dust engulfing the distribution of orbitaldebris, the specific kind of dust formulated to generate a shock on thesurfaces of debris pieces of the distribution of orbital debris, theshock increasing the drag on the distribution of orbital debris toinduce reentry of the distribution of orbital debris.
 2. The method asin claim 1 wherein said deploying comprises: equipping the spacecraftwith the specific kind of dust.
 3. The method as in claim 1 wherein saiddeploying comprises: determining a debris orbit and an edge of thedistribution of orbital debris; setting the spacecraft in a pre-selectedorbit with respect to the debris orbit; and configuring the spacecraftto release the specific kind of dust in the debris orbit at the edge,the specific kind of dust being released in a second pre-selected orbitin relation to at least a portion of the of orbital debris.
 4. Themethod as in claim 3 further comprising: selecting the specific kind ofdust based on dust properties, the dust properties causing a rate ofdecay of the orbit altitude of the specific kind of dust to be roughlysynchronized with a rate of decay of the distribution of orbital debris.5. The method as in claim 1 further comprising: determining an amount ofthe specific kind of dust based on an expected spatial extent of thespecific kind of dust, the position of the distribution of orbitaldebris, and the amount of time of the interaction of the specific kindof dust with the distribution of orbital debris.
 6. The method as inclaim 5 further comprising: determining the orbital lifetime of thespecific kind of dust based on the dust properties.
 7. The method as inclaim 5 further comprising: adjusting the characteristics of thespecific kind of dust to affect a pre-selected subset of thedistribution of orbital debris.
 8. The method as in claim 1 furthercomprising: changing the altitude of the distribution of orbital debristo a pre-selected altitude, the pre-selected altitude being sufficientto deorbit the distribution of orbital debris based on the Earth'snatural drag.
 9. A system for inducing rapid reentry of orbital debriscomprising: means for determining a forward edge location of thedistribution of orbital debris, the distribution of orbital debrishaving an edge of pre-selected altitude; and means for intentionallydeploying, from a spacecraft, a specific kind of dust in a series ofnon-forceful releases, the specific kind of dust intersecting theforward edge location of the distribution of orbital debris, thespecific kind of dust engulfing the distribution of orbital debris, thespecific kind of dust formulated to generate a shock on the surfaces ofdebris pieces of the distribution of orbital debris, the shockincreasing the drag on the distribution of orbital debris to inducereentry of the distribution of orbital debris.
 10. The system as inclaim 9 wherein said means for deploying comprises: means for equippingthe spacecraft with the specific kind of dust.
 11. The system as inclaim 9 wherein said means for deploying comprises: means fordetermining an orbit altitude band of the distribution of orbitaldebris; means for delivering the spacecraft to approximately apre-selected orbit; and means for configuring the spacecraft to releasethe specific kind of dust into the orbital altitude band at the forwardedge location, the specific kind of dust rotating in a pre-selectedrelation to at least a portion of the distribution of orbital debris.12. The system as in claim 11 further comprising: means for selectingthe specific kind of dust based on dust properties, the dust propertiescausing a rate of decay of the orbit altitude of the specific kind ofdust to be roughly synchronized with a rate of decay of the distributionof orbital debris.
 13. The system as in claim 9 further comprising:means for determining an amount of the specific kind of dust based on anexpected spatial extent of the specific kind of dust, the position ofthe distribution of orbital debris, and the amount of time of theinteraction of the specific kind of dust with the distribution oforbital debris.
 14. The system as in claim 13 further comprising: meansfor determining the lifetime of the specific kind of dust based on dustproperties.
 15. The system as in claim 13 further comprising: means foradjusting the characteristics of the specific kind of dust to affect apre-selected subset of the distribution of orbital debris.
 16. Thesystem as in claim 9 further comprising: means for changing the altitudeof the distribution of orbital debris to a pre-selected altitude, thepre-selected altitude being sufficient to deorbit the distribution oforbital debris based on the Earth's natural drag.